Gas Pressure Requirements; Millivolt System Check - USSC 9660 User Manual

The number one cause of all operating
problems with gas appliances is
improper gas pressure!
Such problems as changes in flame
color or configuration, gas pilot or burner
outages, intermittent operation, changes in
heat output, excessive burner noise, etc.,
are nearly always the result of changes in
gas pressure or improper gas pressure at
the time of the installation.
DESIRED
PRESSURE
NATURAL 7.0" W.C.
L.P. 11.0" W.C.
*For the Purpose of Input Adjustment.
The millivolt system and individual
components may be checked with a
millivolt meter having a 0-1000 MV range.
Before checking the system, be certain the
wall thermostat lead wire does not exceed
the length recommended in the Wiring
Section Table, and all connections are
clean and tight.
Conduct each check shown in the
chart below by connecting meter test leads
to terminals as indicated. All readings are
closed circuit.
A. TEST RESULTS
If the reading is more than 100 millivolts
and the automatic valve does not come on,
replace the valve operator. If the closed
circuit reading is less than 100 millivolts,
determine the cause by preceding with
steps "B" and "C".
USSC

GAS PRESSURE REQUIREMENTS

The most important item to check
during the initial installation and the first
thing to check when operating problems
occur is gas pressure!
Gas supplies normally enter a typical
residence at 1/2 PSI (13"-15"W.C.) (3.KPA).
A regulator is then placed inside the
residence which drops this pressure to 7"
W.C. (1.8KPS) (Nat. Gas).
This "inches to inches" regulator is of
adequate capacity to service the gas
appliances such as water heater, dryer,
furnace, etc.
MINIMUM MAXIMUM
PRESSURE PRESSURE
5.0" W.C.* 10.5" W.C.
10.0" W.C.* 13.0" W.C.

MILLIVOLT SYSTEM CHECK

Component Connect
Check Meter Test
Leads To
Terminals
Valve Operator
System 2 & 3
Wall
Thermostat 1 & 3
Thermopile
and Magnet 1 & 2
B. TEST RESULTS
If "B" reading is less than 325 MV, clean
and tighten all electrical connections and
adjust pilot if necessary to increase millivolt
output. If unable to adjust to at least the
specified minimum, change the thermopile.
When proper thermopile output is obtained,
the magnet may then be checked. With
pilot in operation, allow meter reading to
stabilize. Extinguish pilot burner and note
meter reading at dropout point of magnet.
If magnet remains locked up to a reading
of 120 MV or less, the magnet is good.
NOTE: DIAGRAMS & ILLUSTRATIONS NOT TO SCALE
If this regulator's capacity is not
sufficient to add the Model 9660, an
additional "inches to inches: regulator must
be installed specifically for the fireplace.
EXCEPTION: some codes allow 2 PSI
(1.4KPA) supplies to enter the residence,
in which case "pounds to inches" regulators
are used.
The following
information on correct gas pressure
requirements. Be sure your gas supplier
or plumber carefully follows this table
when installing your gas appliance.
MANIFOLD
PRESSURE
3.5" W.C.
10" W.C.
Wall Meter
Thermostat Reading
Contacts Should Be
Should Be
Greater Than
Closed 100 MV
Less Than
Closed 80 MV
Greater Than
Open 325 MV
C. TEST RESULTS
If "C" reading is more than that specified
for the system being checked, clean and
tighten thermostat leads and connection,
shorten lead wires if possible or use heavier
gauge wire. Rapidly cycle thermostat to
clean contacts, or change the thermostat.
table provides
AIR SHUTTER
POSITION
5/16" OPEN
5/16" OPEN
See
Check
Results
Below
A
C
B
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